Flexible Graphene Field-Effect Transistors With Extrinsic ${f}_{{{\mathrm{max}}}}$ of 28 GHz

Graphene field-effect transistors (G-FETs) on flexible substrates have demonstrated much higher strain limits than that on rigid substrates. In this letter, G-FETs with an extrinsic ${f}_{\textrm {max}}$ of 28 GHz on flexible polyethylene terephthalate (PET) substrates are presented. Polyimide film benzocyclobutene with 50-nm thickness is coated on a PET substrate surface for optimizing the carrier transport. The results show that the hole mobility can reach up to 1738 cm 2 /V.s. An Au-supported graphene transfer technology is used to facilitate the quality of graphene in G-FETs and reduce the output parasitic resistance to $50~\Omega $ . The measured figure of metric of “ ${f}_{\textrm {max}}\cdot {L}_{\textrm {g}}$ ” is $8.4~\textrm {GHz}\cdot \mu \text{m}$ , which is 105% higher than the highest reported results on polymeric substrates. The RF performance of flexible G-FETs under the bending condition is also studied. The results of the letter will be useful for developing the millimeter-wave flexible graphene integrated circuits.